Ductwork is utilized to facilitate the heating, ventilation and cooling of various buildings, both residential and commercial. The ductwork typically comprises individual duct sections which are then coupled together to form a continuous, largely airtight duct for conveying a moving mass of air.
The duct sections are typically made from strong, yet relatively light, material such as sheet metal, or the like. It is an important design characteristic that the duct remain as lightweight as possible in order to minimize the size and weight of fasteners and other structural components required to support the ductwork, as well as maintaining materials and fabrication costs of the ductwork itself at reasonable costs.
Commonly utilized ductwork often have rectangular, circular or oval cross sections, and are frequently manufactured and supplied in pre-cut lengths or sections with transversely outwardly protruding interconnection flanges, provided at opposite longitudinal ends of the section, to facilitate interconnecting duct sections at a job site and thus form the finished air conveying ducts of desired lengths.
Whatever the size or shape of the ductwork, the relatively small thickness of the walls of the ductwork, as compared to its cross-sectional dimensions, results in the duct walls being rather flexible. Conventional ductwork may therefore experience large, possibly destructive and oftentimes loud structural deformations if static or dynamic air pressure differentials between the interior and the exterior of the ductwork exceeds a predetermined threshold value. For this reason, mechanical engineering standards, as well as most building codes, require that certain ductwork be reinforced against expansion and/or collapse.
One known reinforcement mechanism for ductworks is shown in FIG. 1 and includes a threaded tie rod 2 oriented between opposite planar sides of a rectangular duct 4. Fixed, inner washers 6 are disposed adjacent the interior side of the opposing duct walls 4, while exterior washers 8 are disposed on the exterior of the duct walls 4 in matching relation to one another. As shown in FIG. 1, a threaded nut 10 is screwed down against each of the exterior washers 8 to secure the reinforcing tie rod in position.
There are several variations of the reinforcing mechanism shown in FIG. 1 and these variations may also include rubber o-rings or other elastic sealing devices disposed between the washers and the duct walls. Moreover, it is also known to replace the fixed, inner washers 6 with threaded nuts or lock nuts which may then be tightened in association with the tightening of the exterior threaded nuts 10 to provide the necessary rigidity to the reinforcing mechanism.
FIG. 2 illustrates a cross-sectional view of another known reinforcing mechanism which is comprised of a metallic tube 10 and an insert 12. After the insert 12 has been disposed within the tube 10, the tube 10 is crimped so as to deform in a radially inward direction. The crimped section of the tube 10 becomes locked within an annular groove 14 which has been inscribed about the periphery of the insert 12, thus locking the insert 12 within the tube 10. A threaded bolt 14 extends from the insert 12 and would extend beyond the exterior of a duct wall to be secured thereto via a threaded nut, or the like. The insert 10 may also include an inner cavity to accommodate an unillustrated biasing member, such as a spring, wherein the spring would outwardly bias the bolt 16 for greater flexibility. The insert 12 may be made from a metallic material or from a plastic or polymer material.
While these known reinforcing mechanisms are successful to a degree, they suffer from several logistical problems. The threaded tie rod 2 shown in FIG. 1 is expensive to produce and deploy in a duct of any length. Similarly, the insert 12 shown in FIG. 2 is also prohibitively expensive.
With the forgoing problems and concerns in mind, it is the general object of the present invention to provide a duct reinforcing rod which overcomes the above-described drawbacks while maximizing effectiveness and flexibility in the assembling process.